This invention relates to apparatus for applying a soldering paste to discrete spots on components prior to soldering, particularly components for use in electrical communications equipment from a bath holding the soldering paste.
For the spot application of soldering paste a known procedure involves the use of metering devices comprising cartridges filled with the paste. The paste is squeezed out of the cartridges through small nozzles and thus applied to the spots that are to be soldered. If a number of closely spaced spots are thus to be wetted with the soldering paste, the known metering devices cannot be used because there is insufficient space for the accommodation in close juxtaposition of a major number of cartridges and of their nozzles. In such a case a single cartridge supplying a plurality of nozzles must be employed. However, in practice it has been found that the branching network of pipes then tends to become clogged within a short period of use, depending substantially upon the grain size and type of the flux and the drying time of the paste. A significant factor is also the diameter of the nozzles. The risk of clogging can be reduced if the grain size of the flux is less than 20 microns. However, this is not an economical proposition. Clogging still occurs even when the grain size has been thus reduced. The employment of cartridges and delivery nozzles is not therefore suitable for mass production methods.